The invention relates to a tank having a piston pressurized by hot gas.
The invention applies particularly but not exclusively to the context of pressurizing a liquid propellant tank of the kind used for example in tactical or strategic missiles.
Document U.S. Pat. No. 3,494,513 describes a tank of this type. The tank has a piston suitable for moving under the effect of thrust from a gas so as to reduce the volume of a chamber containing a liquid, thereby causing the liquid to be expelled from the chamber via an opening formed in the end of the tank.
The chamber containing the liquid propellant is defined by a telescopic metal bladder that is initially folded in accordion fashion to present a series of folds that unfold progressively under thrust from the gas.
That mechanism presents several drawbacks.
Firstly, the telescopic arrangement of the bladder is complex to implement and can be applied only to tanks that are of conical shape.
Furthermore, on unfolding, the bladder cannot come extremely close to the inside walls of the tank, so a non-negligible quantity of liquid is not expelled from the tank.
Above all, that metal bladder system cannot be used in a tank that is pressurized by using hot gas, since the metal bladder does not act in any way as a thermal barrier. This has two consequences: firstly the wall of the tank is heated, and secondly the gas cools so its pressure drops. In a two-stage propulsion mechanism, it then becomes necessary to repressurized the gas between the two stages.